-
Notifications
You must be signed in to change notification settings - Fork 30
/
ReflectiveExtensionSupplier.java
73 lines (65 loc) · 2.48 KB
/
ReflectiveExtensionSupplier.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
/*
* Copyright 2019 The Exonum Team
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.exonum.binding.core.runtime;
import com.google.common.base.MoreObjects;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.util.function.Supplier;
import org.pf4j.ExtensionPoint;
/**
* A reflective supplier of service modules that instantiates them with a no-arg constructor.
*/
public final class ReflectiveExtensionSupplier<T extends ExtensionPoint> implements Supplier<T> {
private final Class<? extends T> extensionClass;
private final MethodHandle extensionConstructor;
/**
* Creates a module supplier for a given service module class.
*
* @throws NoSuchMethodException if the constructor of given service module class does not exist
* @throws IllegalAccessException if accessing the no-arg module constructor failed
*/
public ReflectiveExtensionSupplier(Class<? extends T> extensionClass)
throws NoSuchMethodException, IllegalAccessException {
this.extensionClass = extensionClass;
MethodHandles.Lookup lookup = MethodHandles.privateLookupIn(extensionClass,
MethodHandles.lookup());
MethodType mt = MethodType.methodType(void.class);
extensionConstructor = lookup.findConstructor(extensionClass, mt);
}
@Override
public T get() {
return initializeExtension();
}
@SuppressWarnings("unchecked")
private T initializeExtension() {
try {
return (T) extensionConstructor.invoke();
} catch (Throwable throwable) {
String message = String
.format("Cannot instantiate extension of class %s using constructor %s",
extensionClass, extensionConstructor);
throw new IllegalStateException(message, throwable);
}
}
@Override
public String toString() {
return MoreObjects.toStringHelper(this)
.add("extensionClass", extensionClass)
.add("extensionConstructor", extensionConstructor)
.toString();
}
}